Asthma attacks do not usually come on without warning. Most times, they build slowly. Checking your peak flow can tell you if an attack is coming, sometimes before you have any symptoms.
What is peak flow?
Peak flow can tell you how well you blow air out of your lungs. If your airways are narrow and blocked due to asthma, your peak flow values drop.
You can check your peak flow at home with a small, plastic meter. Some peak flow meters have tabs on the side that you can adjust to match your action plan zones (green, yellow, red). If your meter does not have these, you can mark them with colored tape or a marker.
Write down your peak flow numbers.
Write down your peak flow scores (number) on a chart or diary. Most times, these charts come with your peak flow meter. Make a copy of your chart to bring with you when you see your doctor.
Next to your peak flow number also write:
Any signs or symptoms you felt
Steps you took if you had symptoms or your peak flow dropped
Changes in your asthma drugs
Any asthma triggers you were exposed to
Use your peak flow meter every day.
Once you know your personal best, take your peak flow at:
Every morning when you wake up, before you take medicine. Make this part of your daily morning routine.
When you have asthma symptoms or an attack.
Again after you take medicine for the attack. This can tell you how bad your asthma attack is and if your medicine is working.
Any other time your doctor tells you to.
Check to see which zone your peak flow number is in. Do what your doctor told you to do when you are in that zone. This information should be in your action plan.
Do your peak flow three times and record the best value every time you check it.
If you use more than one peak flow meter (such as one at home and another one at school or work), be sure that all of them are the same brand.
National Asthma Education and Prevention Program Expert Panel Report 3: Guidelines for the Diagnosis and Management of Asthma. Rockville, MD. National Heart, Lung, and Blood Institute, US Dept of Health and Human Services; 2007. NIH publications 08-4051.
National Asthma Education and Prevention Program. How to use a peak flow meter. How to use a metered-dose inhaler. http://www.nhlbi.nih.gov/health/public/lung/asthma/asthma_tipsheets.pdf. Accessed May 8, 2014.
Denis Hadjiliadis, MD, Associate Professor of Medicine, Pulmonary, Allergy, and Critical Care, Perelman School of Medicine, University of Pennsylvania, Philadelphia, PA. Also reviewed by David Zieve, MD, MHA, Isla Ogilvie, PhD, and the A.D.A.M. Editorial team.